1. Field of the Invention
The invention relates in general to respirators and in particular to a new and useful lung-controlled membrane valve for compressed gas respirators with a bushbutton for actuating the valve.
2. Description of the Prior Art
In lung-controlled membrane valves for compressed gas respirators, means are usually supplied which permit manual actuation for opening and closing the normally lung-controlled valves. It is to be assured thereby that the respirator wearer can be supplied with respiratory air also when the negative pressure (vacuum) required for actuation--which is supplied by the pulmonary force--is no longer sufficient. This may be the case, for example, when the membrane seizes or the mechanical transmission system is damaged.
All known devices have the disadvantage that the air supply after manual actuation depends on the mechanical ability of the valve to function.
A known lung-controlled membrane valve for compressed gas respirators is fitted, at a rubber or plastic covering with which the membrane-protecting cover is covered, with a push button for actuation of the membrane. Said pushbutton is provided with a snap button type projection toward the membrane and traversing the membrane-protecting cover. In the inoperative state, the projection does not touch the membrane. When depressing the pushbutton, the projection is pressed against the member and flexes it to the extent that the control lever contiguous to it is actuated and the lung-controlled valve is opened. It is thereby possible to supply the respirator wearer with air when the automatic supply fails, e.g. due to jamming of the membrane or of the lever system. A disadvantage of this arrangement is the necessity that the valve including the transfer from the membrane to the actual valve must be operable. Should the control lever be broken or the closing stud blocked, actuation of the membrane by means of the pushbutton cannot open the valve (German Patent No. 1 080 404).
A further known oxygen respirator has, in addition to a flushing device, a lung-controlled oxygen supply valve, which can be opened by finger pressure, so that oxygen can enter the respiratory cycle from the oxygen bottle independently of the pressure from respiration. The oxygen supply valve is a membrane valve. Between the protective cover and the membrane, a leaf spring under tension is arranged, which can assume a position arched outwardly toward the protective cover or inwardly toward the membrane. In the arched inwardly state, it maintains the oxygen supply valve open by pressure on the membrane and a control lever. The protective cover has a central opening, through which, when taking into operation, e.g. by actuation with the finger, the leaf spring is pressed inward and thereby the valve is opened. After the intended pressure has been reached, the leaf spring is pushed into its inoperative position by the membrane. The lung-controlled membrane valve then operates normally. What is disadvantageous is that oxygen supply is not assured if the control lever or other elements of the lever linkage should break or jam, because the possibility of control via the leaf spring presupposes a functioning valve arrangement. (German Patent No. 1 257 585).